Semiconductor processes may utilize induction heating to heat a wafer to high temperatures (˜1000° C.). In induction heating, an alternating current in an inductor coil induces eddy currents in a nearby conducting material called a susceptor, which is in close proximity to a substrate/wafer. These eddy currents generate heat within the susceptor and cause the temperature of the susceptor to rise. The susceptor in turn radiates heat in net to its surroundings. A portion of this net radiated heat flux is absorbed by the wafer and causes the wafer temperature to rise. As the wafer increases in temperature, it also loses heat to its surroundings. When the heat absorbed balances the heat lost by the wafer, the wafer temperature stabilizes.
An important concern when heating a wafer is the thermal uniformity of the wafer in equilibrium. The uniformity depends on the radiated heat from the susceptor, which in turn depends on the power density profile induced by the inductor coil. The temperature profile of the wafer will closely match the power density profile of the inductor coil. It is very difficult to obtain a uniform power density profile in most cases. Common solutions, such as locating the wafer eccentrically to the susceptor and rotating the wafer, typically involve the addition of complicated, expensive hardware.
It is in this context that embodiments of the invention arise.